The present invention relates to a liquid crystal display device and more particularly to the structure and the driving method of the display device which provides a high-quality display.
The conventional liquid crystal display device is constructed to have an active matrix substrate and a light-screening mask formed thereon so that the display device can provide a high-contrast panel as disclosed in JP-A-1-297623. This construction, however, has a shortcoming that the application of the construction to, in particular, a high-definition liquid crystal display device results in lowering a contrast ratio.
As disclosed in JP-A-2-10955, a storage capacitance element may be provided in parallel to a liquid crystal unit so as to suppress reduction of stored charges resulting from leakage current of a thin film transistor or a liquid crystal unit and diminish variation of an effective voltage. However, this storage capacitance element also has some difficulty in working the form of each element located on the substrate to be uniform on the plane of the substrate if the liquid crystal device is required to be more definitive and larger in size, resulting in disadvantageously making the dimensions of the elements provided on the substrate variable. The variation leaves an after image on the display device and degrades the liquid crystal.